The invention relates generally to a process for the production of coke. Of particular interest to the invention is the production of premium coke, which is also referred to as acicular coke.
Premium or acicular coke is, in particular, characterized by a good convertibility to graphite. Important characteristics of such coke are as follows (compare the publication by Winnacker, Kuchler entitled "Chemische Technologie" and published by Carl Hanser of Munich, Germany in 1970; vol. 1 (Anorganische Technologie), page 474):
______________________________________ Density after annealing 2.0 - 2.17 grams per cubic at 1300.degree. C: centimeter Coefficient of thermal 4.5.10.sup.-6 -- 5.5.10.sup.-6 per .degree. C expansion after anneal- -ing at 2700.degree. C: Convertibility to graphite: 1.45 - 1.65 ______________________________________
A process for the production of anisotropic coke which is readily converted into graphite is already known. Here, bituminous coal-tar pitch is mixed with an aromatic diluent which is derived from petroleum or bituminous coal-tar. The portions of the pitch which remain in the form of solid particles are removed from the resulting mixture by decanting, filtering or other separating procedures at a temperature of approximately 150.degree. C. The thus-clarified mixture is then coked and calcined at temperatures of 1450.degree. to 1500.degree. C using the delayed-coking process. The delayed-coking process resides in that, starting at about 350.degree. C, the pitch is coked within a period of approximately 24 hours while increasing the temperature to about 1550.degree. C.
This method for the preparation of coke possesses certain disadvantages. Thus, extensive and time-consuming operations are required for the production of the starting product from which the coke is derived. For instance, the diluent must be driven off and there are great technical problems associated with the distillation stage. Moreover, a complete removal of the diluent is not possible in practice. As a result, residual diluent is driven off in the apparatus used for the delayed-coking procedure and this causes disturbances in the coking apparatus.